Group Ironman is now available in OSRS and is described as “Ironman with a little help from your friends”.
Groups of two to five players can join up and participate in this new Ironman format. Groups can share resources, use the new group storage and visit each other’s houses.
There is also a Group Ironman Leaderboard so you can compete with other groups about who is the most Ironmanest.
More info about Group Ironman can be found in the official post.